Normal grain growth(110)(001)textured iron-cobalt alloys

ABSTRACT

1. AN ALLOY MEMBER WHICH EXHIBITS IMPROVED PERMEABILITIIES AT LOW FIELD STRENGTHS RESULTING FROM CRYSTALLOGRAPHIC ORIENTATION COMPARED TO UNORIENTED MAGNETIC MATERIAL OF THE SAME COMPOSITION CONSISTING ESSENTIALLY OF FROM ABOUT 5% TO ABOUT 35% COBALT, UP TO 2% CHROMIUM, UP TO 1% MANGANESE, UP TO 3% SILICON, LESS THAN 0.005% SULFUR AND THE BALANCE ESSENTIALLY IRON WITH INCIDENTAL IMPURITIES, THE ALLOY HAVING A PRIMARY RECRYSTALLIZED GRAIN STRUCTURE IN WHICH A MAJOR PROPORTION OF THE GRAINS EXHIBIT A (110) TEXTURE AND IN WHICH A MAJOR PROPORTION OF THE ORIENTED GRAINS HAVE CUBE EDGES OF THEIR CRYSTAL LATTICES ALIGNED WITHIN 10* OF THE ROLLING DIRECTION.

Oct. 22, 1974 Filed Feb. 22, 1972 ToRouE,ERss/ :M

D. R. THORNBURG HAL NORMAL GRAIN GROWTH (110) [001] TEXTURED IRON-COBALTALLOYS I 4 Sheets-Sheet 1 M849 AND M853-ANNEALED I35 3%Si-Fe 48 HOURS AT900C ORIENTED I THICKNESS PEAK SAMPLE (IN) RATIO 3/os| Fe 9o I ORIENTEDM8 0342 1 M853 -o.0I2I 0.370

I M849, 0.0l 0.548 I 45 |8O I I I l 0 90 I35 I ANGLE BETWEEN FIELD ANDROLLINGIDIRECTION (DEGREES) IFIGI NORMAL GRAIN GROWTH (110) [001]TEXTUREDIRON-GOBALTALLOYS Filed Feb. 22, 1972 1974 D. R. THORNBURG 4Sheets-Sheet 2 FIG Oct. 22, 1974 THQRNBURG EI'AL 3,843,424

NORMAL GRAIN GROWTH (110) [001] TEXTURED IRON-COBALT ALLOYS Filed Feb.22, 1972 4 Sheets-Sheet 3 FIG.4

Oct. 22, 1974 R- THORNBURG ETAL 3,843,424

NORMAL GRAIN GROWTH (110) [001] TEXTURED IRON-COBALT ALLOYS Filed Feb.22, 1972 4 Sheets-Sheet 4 United States Patent O1 fice 3,843,424Patented Oct. 22, 1974 3,843,424 NORMAL GRAIN GROWTH (110) [001]TEXTURED IRON-COBALT ALLOYS Donald R. Thornburg and Karl Foster,Pittsburgh, Pa.,

assignors to Westinghouse Electric Corporation, Pittsburgh, Pa.

Filed Feb. 22, 1972, Ser. No. 228,071 Int. Cl. H01f 1/00 US. Cl. 148-1206 Claims ABSTRACT OF THE DISCLOSURE An alloy and a method for producingthe same are described in which the alloy is characterized by aprimarily recrystallized microstructure having a (110) [001]orientation. The alloy contains from to 35% cobalt, up to 2% chromium,up to 3% silicon, less than 0.005% sulfur and a balance essentially ironwith incidental impurities. The method includes a schedule of hot andcold working the latter in limited amounts together with correspondingheat treatments producing the desired improved magnetic characteristics.

CROSS REFERENCE TO RELATED APPLICATIONS The present application isclosely related to application Ser. No. 228,319, filed Feb. 22, 1972 andapplication Ser. No. 228,070, filed Feb. 22, 1972 each of whichapplication is presently pending.

BACKGROUND OF THE INVENTION [Field of The Invention The presentinvention relates to iron-cobalt alloys having improved magneticcharacteristics and a method for producing said alloys. The alloys arecharacterized by having a high grain volume of (110) ][001] orientationtexture, the same having been derived by means of primaryrecrystallization and normal grain growth.

Description of The Prior Art The operating inductions of large portionsof todays transformers are limited by the saturation value of orientedsilicon steel, that is, a steel containing about 3% silicon and whichhas a high degree of (110) [001] orientation. This saturation value isgenerally taken to be about 20,300 gauss. Both from an economic and atechnological standpoint this is the highest quality transformermaterial presently available commercially. v

Cobalt functions in iron to significantly increase the saturation valueof the iron, and saturation inductions on the order of 24,000 gauss areobserved in cobalt-iron alloys containing 25 to 50% cobalt. The alloyscontaining from about 35 to 50% cobalt have a low magnetocrystallineanisotropy and the lowest values occur in the range of about 50% cobalt.Consequently, high inductions are obtained at low field strengths. It isnoted however that when the cobalt content in the alloy is increased toa value ranging from more than about 35% and up to about 80% by weight,with a corresponding decrease in the iron content, the alloy undergoesatomic ordering. Consequently, high cobalt-iron alloys such as the 50%cobaltiron alloy are quite brittle and can only be cold worked after adrastic quench resulting in high production costs.

While considerable ductility is observed in alloys containing less than35 cobalt which alloys do not undergo atomic ordering, the highinduction values for low field strength have never been observed in thisalloy most likely because of their high positive anisotropy values.However, the improved ductility makes the alloys containing betweenabout 5% and about 35% cobalt quite attractive from an economicmanufacturing point of view.

Heretofore, there have been commercially available alloys containingabout 27% cobalt in an iron base. However, these alloys, while showingsome improvement in the overall saturation induction value, nonethelesswere deficient from the standpoint of having low inductions at low fieldstrengths. Consequently, such material only found limited use where itwas designed for operation at near the saturation value. While thepresence of between about 5% and about 35% cobalt in an iron matrix willprovide improved saturation values, by the present invention it has beenfound that proper processing makes it pos- .sible to develop grainorientation such that high inductions are obtained at low fieldstrengths without adversely affecting the coercive force or of thesaturation induction values. The method as applied to the alloy of thepresent invention is effective for producing such results which aremanifest in the observed magnetic characteristics.

Summary of The Invention The present invention relates to an alloy whichcontains in weight percent between about 5% and about 35% cobalt, up toabout 2% chromium, up to about 1% manganese, up to about 3% silicon andthe balance iron with incidental impurities. A critical aspect of theinvention is recognizing and controlling the sulfur content thereof to avalue of less than about 0.005% and preferably less than about 0.002%.

The method for obtaining the improved magnetic characteristics in thesealloy compositions includes an initial step of hot working of the metalat a temperature of between about 1000 C. and about 1100 C. to a desiredintermediate gauge and thereafter a critical cold working the alloy inone or more steps to the desired final gauge and a final criticalprimary recrystallization anneal. While any hot working will sufficesince it is not a critical point in the process, hot rolling ispreferred. It has been found that in order to develop the desiredmagnetic characteristics, at least the last cold working operation tofinal gauge must effect a reduction in the cross sectional area rangingbetween about 40% and about and the alloy is preferably heated rapidlyto the recrystallization temperature and finally subjected to a hightemperature heat treatment which results in the development of aprimarily recrystalliZed microstructure having a majority of the grainsdisplaying an orientation described as [001] in Miller Indices, and themajority or a high proportion of the grains have the cube edges of theircrystal lattices parallel within 10 to the direction of rolling of thesheet or strip of the alloy. The final high temperature heat treatmentto which the alloy is subjected usually takes place at a temperaturebetween about 800 C. and the A temperature of the alloy undergoing thefinal heat treatment. Preferabbly the final heat treatment is conductedin a protective atmosphere, such as an atmosphere of substantially purehydrogen having a dew point of less than about 40 F.

DESCRIPTION OF THE DRAWINGS magnification of magnification ofmagnification of magnification of magnification of DESCRIPTION OF THEPREFERRED v EMBODIMENT Generally speaking, the present invention relatesto an alloy having improved magnetic characteristics, and which has acomposition containing from about to about 35% cobalt, at least oneelement which is effective for raising the volume resistivity such as upto about 2% chromium, and up to about 3% silicon, less than about 0.005%sulfur, up to about 1% manganese, and the balance essentially iron withincidental impurities. The alloy in its fabricated form is characterizedby having a primarily recrystallized-grain structure in which a majorityof the grains possess a (110) [00 1] texture.

. Within the broad chemical analysis set forth hereinbefore a preferredembodiment contains between about 8% and about 20% cobalt, from about0.5% to about 2.0% silicon, a sulfur content of less than about 0.005%and the balance iron with incidental impurities. Another preferredcomposition contains cobalt within the range between about 20% and about30%, chromium within the range between about 0.25% and about 1%, lessthan about 0.005% sulfur and the balance essentially iron with thenormal impurities. Outstanding results have been obtained where thecobalt content is maintained within the range between about 26.5% andabout 28%, from about 0.25% to about 0.75% chromium, less than about0.002% sulfur and the balance iron with incidental impurities. Thislatter compositional range has improved magnetic characteristicsincluding a high saturation value, as well as high inductions at lowfield strengths thereby resulting in an outstanding combination ofmagnetic characteristics. Excellent magnetic materials have also beenobtained where the cobalt content is maintained within the range betwe nabout 10% and about 18% cobalt, from about 0.5% and about 2.0% silicon,less than about 0.0025% sulfur with the balance being essentially ironwith incidental impurities. While ttu's latter alloy will have greaterresistivity from the standpoint of the inclusion of the silicon contentand slightly lower saturation induction values, nonetheless thedegree oforientation is outstanding so as to given exceedingly high B value whichis a measure indicative not only of the degree of orientation but alsois indicative of the attainment of high inductions at low fieldstrengths. Consequently, the various combina tions of magneticcharacteristic obtainable in each of the ranges set forth. hereinbeforetogether with the simplified processing for obtaining these desirableresults makes the same quite economically attractive compared withcommercially available oriented 3% silicon-iron.

It is noted that the alloy of the present invention must be criticallycontrolled with respect to the sulfur content. In this respect. it hasbeen noted that the majority of the grains will developthe requireddegree of orientation provided the initial sulfur content within themelt is limited to about 0.005% maximum. As will be set forth more fullyhereinafter no special desulfurizing heat treatments are performedduring the manufacture of the alloy to its desired finished gaugeproduct. Accordingly, it becomes exceedingly important and in factcritical to maintain the sulfur content at less than about .005 andpreferably less than about 0.0025 Exceedingly good results have beenobtained where the sulfur content has been limited to a value notinexcess of about 0.002%

It will be noted that where silicon is not added as a deliberatealloying element, as for example, where the cobalt content is maintainedwithin the range between about 20%. and about 35%., it is desirable tohave the silicon content at a value of less than about 0.25%. Whilesilicon is noted for its effect of improving volume resistivity it hasbeen found that other elements such as chromium, vanadium, aluminum,titanium and molybdenum are more effective where the cobalt content iswithin the range between 20 and 35%. Consequently, the alloying siliconaddition is preferred only where the cobalt is less than about 20%. Anyelement which is soluble and does not form a'second phase will improvevolume resistivity; however care must be exercised so that the otherproperties are not detrimentally afiected. By the same token, it hasalso been found that it is preferred, although not critically necessary,to have the manganese content at a value of less than about 0.50%.Where, however, silicon is added as an alloying component, for example,in an alloy with a cobalt content of between 8% and 20% for improvedresistivity, the manganese may be quite lownominally about 0.05%.

While during normal processing of the alloys into finished gaugematerial the alloy may be subjected to a decarburizing anneal,nonetheless it is preferred to maintain the carbon content at less thanabout 0.030% with a correspondingly low content of oxygen and thebalance of the other incidental impurities. Typical levels of theseelements may include about 0.003% oxygen, about 0.05% manganese, about0.1% silicon and the balance essentially of iron. Such levels ofincidental impurities are ob tained by vacuum induction melting; howeverother melting methods may be employed with equal success.

The alloy having the desired composition is subjected to a hot workingoperation and one or more cold working operations in order to reduce thealloy to the desired final gauge thicknessl'n this respect it has beenfound that good success has been obtained where the alloy in ingot formis hot worked as by rolling from a temperature within the range betweenabout 1000 C. and about 1100" C. The material is hot worked at thistemperature range to any desired'intermediate gaugethickness such as ahot rolled band gauge of between about 0.075 and about 0.150 inches. Itwill be appreciated that while the intermediate gauge has been setforth, deviations therefrom may be made depending on the finish gaugethickness. Thus the intermediate gauge thickness is selected withrespect to the subsequent cold reductions and finish gauge thickness.

Following hot working at a temperautre within the range between l000 C.and 1100 C. the alloy is heat treated for a time period of about 10minutes to about 60 minutes at a temuperature within the range betweenabout 600 and 900 C. During such heat treatment it is convenient tointroduce a hydrogen atmosphere such hydrogen atmosphere having a dewpoint of greater than about -40 F. in order to decarburize the material.It is desired in some cases to decarburize at the intermediate g augethickness and typical annealing times of about 15 minutes at about 700C. in a hydrogen atmosphere at approximately a +60 F. dew point iseffective for removing about half of the carbon content remaining in thesample following hot working. However, it is also contemplated that suchdecarburizing heat treatment can be delayed to just prior to final heattreatment or cut any other step therebetween. After .the decarburizinganneal, the material is pickled in preparation for cold working.

Cold working is accomplished in one or more operations. Preferably, thecold working is accomplished in two steps. However, it has been foundthat it is necessary that at least the last cold working of the materialto finish gauge must effect a reduction in the cross sectional arearanging between about 40% and about 75%. In this respect it has beennoted that where the final cold reduction is less than about 40% asharply defined [001] texture is not obtained as where the material hasbeen subjected to at least a 40% reduction in cross sectional area.While reductions in excess of 75% will not adversely affect the finaltexture to any marked degree, nonetheless some deterioration has beennoted and the degree of recrystallization may be some-what affectedthereby. Consequently it has been found desirable to limit the coldreduction to finish gauge to avalue between about 40% and about 75% andoutstanding results have been obtained where the final cold reductionhas been effected in an amount ranging between about 50% and about 60%.

- In this respectit should be noted that the initial cold reduction, ifmore than onecold rdeuction stage ,is contemplated, may be effected bymeans of a hot-cold working. That is, the material may be heated to atemperature above ambient temperature but at a temperature below thetemperature at which spontaneous recrystallization takes place duringworking. Thus while the material will be warmed well above roomtemperature it will nonetheless be a cold working and hence has beentermed hotcold working. In this respect it has been found that where theintermediate gauge following 'hot working is for example about 0.100inches in thickness, warm rolling may be effected at a temperaturewithin the range between about 200 C. and about 300 C. to reduce thematerial to a thickness of about 0.040 inches, following which thematerial is permitted to cool to ambient temperature where it is thenfurther cold rolled to about 0.025 inch. Thus the total reduction fromhot rolled band thickness in the first cold rolling stage is effectivefor reducing the cross sectional area about 75%.

In all cases where more than one cold working operation is performed onthe material, an intermediate anneal is preferably employed, saidintermediate anneal being conducted for -a time period of up to abouttwo hours at a temperature in excess of about 800 C. Preferbaly, suchintermediate anneal is performed in an atmosphere of pure dry hydrogen,that is, a hydrogen content having a dew point of less than about 40 F.

Following such intermediate annealing the material is cold worked tofinish gauge, such finish gauge cold working typically effecting a 40 to75% reduction in cross sectional area and outstanding results have beenobtained Where the cold reduction has been limited to a range betweenabout 50% and 60% reduction in cross sectional area. Thus the overallprocessing is not only effective for removing about one-half of theoriginal carbon content but thematerial has been reduced to finish gaugeand thereafter fhwmaterial may be given the final high temperature heattreatment in order to develop the desired degree of oriented graintexture. In this respect it has been found that annealing the materialat a temperature within the range betwene about 800 C. and the Atemperature for a time period between about 12 hours and about 72 hoursin an atmosphere of hydrogen having a dew point of less than -40 F.followed by furnace cooling has been effective for producing anoutstanding degree of grain orientation the same having beenaccomplishedby means of a primary recrystallized grain structure whichhas undergone normal grain growth. It has been found that orientationtextures have been more pronounced where the finish gauge material hasbeen rapidly heated to a temperature of about 800 C'. Consequently, thepreferred mode of processing includes a strip anneal for five minutes at800 C. followed by a final box annealing-at a temperature within therange between 800 C. and the A temperature.

In order to more clearly demonstrate the alloy and the method of thepresent'invention reference may be had to the following Table I whichincludes the chemical composition of a number of heats which were madeand tested in accordance with the present invention together with acommercially available material containing an iron base with about 27%cobalt being present and which was processed employing presentcommercial practices.

The foregoing processing removed about half of the original carbon butthe other additions including sulfur did not change significantly. Thefinish gauge material was cut into Epstein strips in the rollingdirection. In addition a 1 inch'diameter torque disc of each of thealloys was annealed for 48 hours at 900 C. in dry hydrogen andthereafter furnace cooled.

Reference is directed to Table II which includes the DC magneticcharacteristics exhibited by each of the alloys.

TABLE IL-MAGNETIC CHARACTERISTICS Peak torque (ergs/ Torque I I B10 Brnocrnfi) ratio (0a.) (G) (G) 64, 700 0.53 1. 03 18, 400 22,700 53. 4000.61 1.36 17. 300 22, 000 44, 0. 42 1. 59 17, 200 22, 100 131, 0. 45 0.60 19, 300 23, 100 3 138, 000 0. 37 0. 57 19, 600 22, 900 Commercial 27%C Fe (unoriented) l. 70 16, 100 21, 100 Commercial 3% Si-Fe (oriented)167, 000 0. 34 0. l1 18, 300 19, 800

In order to complete the comparison, data is also included on a typicalcommercial heat of a singly oriented 3% silicon steel and a 27%cobalt-iron alloy (unoriented) for comparative purposes. In interpretingthe data set forth in Table II it should benoted that the peak torquevalues in the Table represent the average of the absolute values of thelarge peaks in the curve. The torque ratio represents a ratio of theabsolute values of the small peaks to the large peaks for a given curve.Since the commercially processed 27% cobalt material did not havemeasurable torque peaks and had a B value of only 16,100 gauss suchvalues clearly indicate that the grain texture in the commerciallyprocessed material is essentially random.

From the data set forth in Table II it can be seen from the torquevalues as well as the induction at 10 oersted, substantially highervalues for B have been obtained with each of the compositions. However,the compositions with the lowest sulfur content, that is, heats M 852and M 853 had outstandingly high B values together with peak torquevalues which closely approach the value for:the 3% silicon iron whichhas a high degree of [001] orientation for commercially availablematerial.

This is more clearly demonstrated by reference to FIG. 1 whichsuperimposes the plots of the torque value versus the angle between thefield and the rolling direction in degrees for a highly oriented 3%silicon iron as well as for alloys M 853 and M 849. Thus from the valueof M 853 it can be seen that by decreasingthe sulfur content to acritically low level and by processing the material as set forthhereinbefore torque curves approaching those of. the commerciallyavailable 3% silicon iron are closely approximated. However, bycomparing the saturation values in Table II, that is, the inductionvalues where the field strength is 100 oersted it is clearly seen thatmuch higher saturation induction values are obtained from thecobalt-iron alloys with overall improved magnetic characteristicsresulting from the orientation of the material.

Reference is now directed to FIGS. 2 through 6 inclusive which arephotomacrographs of alloys identified therein and whose composition isset forth in Table I. These photomacrographs are at a magnification of20X after annealing the cobalt iron alloy sheets for 48 hours at 900 C.,and show a strong correlation between the sulfur content and the finalgrain size. From FIGS. 2 through 6 it isv apparent that the low sulfurlevels result in a large grain size by normal grain growth, that is,from a primarily recrystallized microstructure and not as a result ofsecondary recrystallization and grain growth. These results as well asthe shorter annealing times on M 852 and M 853 indicate that the degreeof (110) [001] texture is increased by primary grain growth in alloyscontaining low sulfur. This in direct contrast to the development of asimilar oriented texture in 3% silicon iron where controlled high sulfurlevels are required for texture development by secondary grain growth.Thus alloys M 852 and M 853 reflect the additional beneficial aspectthat the cobalt iron alloys with low sulfur values have low coerciveforce values. Moreover it appears that the addition of chromium to thesecobalt iron alloys appear to improve the textureiorma tion to somedegree while increasing volume resistivity.

Another heat of cobalt iron alloy was melted to substantially the samecomposition as heat M 853. This heat was identified as heat M 903 andwas processed employing substantially the same conditions as heat M 853with the following exception. After annealing for one hour at 900 C. atan intermediate gauge of 0.025 inch, the material was cold rolled tofinal thicknesses of 0.0095 and 0.012 inch.

Reference is directed to Table III which contains the magneticcharacteristics of the heat M 903.

TABLE III.-MA GNE'IIC CHARACTERISTICS Domain pattern texture analysiswere performed on samples of material from heats M 852 and M 903, thelatter. having a finish gauge thickness of about 0.0095 inch. It wasfound that 85% by volume of the grains had the (110) and 7% by volumedisplayed (100) texture, of which such (110) grains had crystal latticeswhose cube edges aligned within 10 of the [001] driection in 80% of thegrains. When the deviation from the [001} or rolling direction wasmeasured within it was found that the edges of the crystal lattices of88% of the (110) grains were within this limitation.

Heat M 852 was given a final cold reduction of just 50%, consequently,it did not develop as high a texture as heat M 903 rolled to 0.0095 inchthickness. Actual measurements of heat M 852 indicated 61% by volume ofthe grains had the (110) texture while 16% exhibited the (100) texture.Further, 58% of the cube edges of crystal lattices of the grainsdeviated less than 10 from the [001] direction and 68% of the grainswere within 15 of the [001] direction.

In each of the forgeoing, the texture developed by means of primaryrecrystallizationv and normal grain growth. In each instance thepresence of the (100) [001] texture does not detract from the magneticcharacteristics exhibited by the alloy containing the preponderatingtexure (110) [001].

These data appear to indicate that a slightly higher degree of finalcold reduction results in an improvement in the texture and thatextremely high induction values are obtained. If the B values as well asthe peak torque values for the heat M 903 at the 9.5 mil stage arecompared with the commercial oriented 3% silicon steel as set-forth inTable II it becomes clear that a higher degree of (110) [001] texturewas obtained in heat M 903' than that in the commercial 3% siliconsteel. Thus the peak torque values are higher, the B values are higherand clearly, as would be expected, the saturation values are near thetheoretical maximum. T r

Another series of heats were made in. which the sulfur content'wascontrolled to very low limits that is, a sulfur content of lessthan 001%by weight. Reference is directed to Table which includes the chemicalcomposition of three heats which were made and tested.

TAB LE IV.CHEMICAL COMPOSITION [Percent by weight] Percent Co Cr Mn Si OS 0 Both disc samples for torque measurements as well as Epstein sampleswere cut from the material which samples were annealed for 48 hours at900 C. in dry hydrogen.

Reference is directed to Table V which lists the magneticcharacteristics of the alloys.

TABLE V.MAGNETIC CHARACTERISTICS Peak torque Torque II B10 Brno Alloy(ergs/cma) ratio (oe.( (G) (G) From the test results set forth in TableV it is noted that high B 'values were obtained indicating a high degreeof (100) [001] orientation. To substantially the same elfect thesaturation values were quite acceptable for the alloys although the peaktorque values were somewhat lower than obtained with the bettermaterials previously set forth herein. It is believed that the thickerhot rolled band material resulting in substantially higher intermediatecold reductions resulted in the somewhat lower peak torque values.Accordingly, it is desired to limit the cold reduction elfected in eachstep to a value within the range between about 40% and about 75% incross sectional area.

From the foregoing it may be noted that each of the alloys which weremade and tested contained a cobalt content near the upper limit. Havingthus found a high degree of orientation being eifected by means of theprocess of the present invention, other cobalt contents wereinvestigated in order to determine the relative level of cobalt whichwould be effective for obtaining improved induction values commensuratewith obtaining the required degree of (100) [001] orientation in aprimarily recrystallized microstructure. -Reference is directed to TableVI which contains the nominal composition of two alloys which were madeand tested in accordance with the teachings of the present invention itbeing noted that the alloys set forth in Table VI contain 18% cobalt and10% cobalt with a corresponding amount of silicon of 1% and 2% beingadded to obtain improved volume resistivity. In these heats, the sulfurcontent was controlled so as to The alloys were processed in accordancewith the following schedule:

hot roll at 1050" C. to 0.080 inch;

pickle; anneal 5 hours at 850 C. in dry hydrogen; cold roll to 0.025inch;

anneal 5 hours at 850 C. in dry hydrogen.

cold roll to 0.011 inch finish gauge thickness.

TABLE VII.MAGNETIC CHARACTERISTICS Peak torque (ergs/ Torque He B BSample cmfi) ratio (e.) (G) M 833 106, 700 O. 44 0. 368 18, 500 21, 700M 887 121, 300 0. 45 O. 275 18, 000 20, 900

The torque values indicate a high degree of (110) [001] texture.Although the 10% cobalt sample appears to be a little more highlytextured, the 18% cobalt alloy has a higher induction value because ofits higher saturation value. These samples exhibited only primaryrecrystallization and normal grain growth. In other tests, much lowertorque values were obtained in similarly processed alloy compositionshaving sulfur additions of 0.01%. Also samples slowly heated to finalannealing temperature, that is, appear to give poorer results.

From the foregoing examples it can be seen that a high degree of 110)[001] texture can be obtained by primary recrystallization and normalgrain growth in cobalt iron alloys over a wide range of cobalt,manganese, silicon and chromium contents. The processing schedule isclearly important and should be noted that the final anneal must be keptbelow the alpha to gamma transformation temperature which isapproximately 950 C. or, in more precise terms, at a maximum temperaturebelow the A temperature. By thus keeping the sulfur content to less than0.005%, highly (110) [001] textured alloys are obtained through primaryrecrystallization and grain growth. Accordingly, transformers androtating magnetic core devices such as motors and generators employingthis material can be made with decreased size and weight resulting insignificant economic advantages in the production of both the alloy andthe apparatus.

We claim:

1. An alloy member which exhibits improved permeabilities at low fieldstrengths resulting from crystallographic orientation compared tounoriented magnetic material of the same composition consistingessentially of from about to about 35% cobalt, up to 2% chromium, up to1% manganese, up to 3% silicon, less than 0.005% sulfur and the balanceessentially iron with incidental impurities, the alloy having a primaryrecrystallized grain structure in which a major proportion of the grainsexhibit a (110) texture and in which a major proportion of the orientedgrains have cube edges of their crystal lattices aligned within of therolling direction.

2. The alloy member of claim 1 in which the cobalt is present in anamount between about 8% and about 20% and the silicon is present withinthe range between about 0.5% and about 2.0%

3. The alloy member of claim 1 in which the cobalt is present within therange between about 20% and about 30% and the chromium is present withinthe range between about 0.25% and about 1.0%.

4. An alloy member which exhibits improved permeabilities at low fieldstrengths resulting from crystallographic orientation compared tounoriented magnetic material of the same composition consistingessentially of from about 26.5% to about 28% cobalt, from about 0.25 toabout 0.75% chromium, less than about 0.002% sulfur and the balance ironwith incidental impurities, the alloy being characterized by a primaryrecrystallized microstructure having a major proportion of the grainsexhibiting a orientation and a major proportion of the oriented grainshaving cube edges of their crystal lattices aligned within 10 of therolling direction.

5. An alloy member which exhibits improved permeabilities at low fieldstrengths resulting from crystallographic orientation compared tounoriented magnetic material of the same composition consistingessentially of from about 10% to about 18% cobalt, from about 0.5 toabout 2.0% silicon, less than about 0.0025 sulfur and the balanceessentially iron with incidental impurities, the alloy beingcharacterized by a primary recrystallized grain structure with a majorproportion of the grains exhibiting a (110) orientation and a majorproportion of the oriented grains have cube edges of their crystallattices aligned within 10 of the rolling direction.

6. An alloy member which exhibits improved permeabilities at low fieldstrengths resulting from crystallographic orientation compared tounoriented magnetic material of the same composition consistingessentially of from about 5% to about 35% cobalt, up to 3% of at leastone element for improving the volume resistivity without detrimentallyaffecting the chemical, physical and mechanical properties of the alloyand selected from the group consisting of silicon, chromium, vanadium,aluminum, titanium and molybdenum, less than about 0.005% sulfur, up to1% manganese and the balance es sentially iron with incidentalimpurities, the alloy having a primary recrystallized grain structurewith a major proportion of the grains exhibiting a (110) orientation anda major proportion of the oriented grains having the cube edges of theircrystal lattices aligned within 10 of the rolling direction.

References Cited UNITED STATES PATENTS 1,247,206 11/1917 Becket 75-123 K2,442,219 5/1948 Stanley 75123 K 3,164,496 1/1965 Hibbard et al. 1481201,678,001 7/1928 Brace 75--123 K 2,717,223 9/1955 Binstock et al 1481222,292,191 8/1942 Brandt et al. 148122 3,695,944 10/1972 Stroble148-31.55 2,112,084 3/1938 Frey et al 14831.55 3,418,710 12/1968 Seidlet al. 148122 3,124,491 3/1964 Foster 148--31.55 3,166,408 1/1965 Chen14831.55 3,347,718 10/1967 Carpenter et al 148-111 3,597,286 2/1968Thornburg 148-121 FOREIGN PATENTS 424,327 1935 Great Britain 148-31551,180,954 1964 Germany 148100 OTHER REFERENCES Bozorth, R. M.: Ferromagnetism, New York, 1951, pp.

WALTER R. SATTERFIELD, Primary Examiner US. Cl. X.R.

1. AN ALLOY MEMBER WHICH EXHIBITS IMPROVED PERMEABILITIIES AT LOW FIELDSTRENGTHS RESULTING FROM CRYSTALLOGRAPHIC ORIENTATION COMPARED TOUNORIENTED MAGNETIC MATERIAL OF THE SAME COMPOSITION CONSISTINGESSENTIALLY OF FROM ABOUT 5% TO ABOUT 35% COBALT, UP TO 2% CHROMIUM, UPTO 1% MANGANESE, UP TO 3% SILICON, LESS THAN 0.005% SULFUR AND THEBALANCE ESSENTIALLY IRON WITH INCIDENTAL IMPURITIES, THE ALLOY HAVING APRIMARY RECRYSTALLIZED GRAIN STRUCTURE IN WHICH A MAJOR PROPORTION OFTHE GRAINS EXHIBIT A (110) TEXTURE AND IN WHICH A MAJOR PROPORTION OFTHE ORIENTED GRAINS HAVE CUBE EDGES OF THEIR CRYSTAL LATTICES ALIGNEDWITHIN 10* OF THE ROLLING DIRECTION.